Studies have shown that gaseous methane can be stored in liquid hydrocarbons for example propane through solute absorption into solution. Propane is cooled down with refrigeration equipment and a condensor coil while the methane is introduced into the propane by means of gas jets. This process is accomplished by considerable increase in pressure. When the pressure is relieved, the methane is flashed out of the mixture as a gas and can be used as a fuel gas. After the methane is utilized the propane then can be vaporized and used also as gas for general fuel requirements. Storage of natural gas by solution under pressure in refrigerated liquefied petroleum gas has been presented as an idea for combining conventional pressure storage tanks and liquefied petroleum-air plant combinations in one system at the same time increasing the storage capacity up to 5 to 6 times for the same volume and pressure. The high solubility of natural gas in liquefied petroleum gas has been used as a storage tool to meet increased consumption requirements and demands on existing storage volume equipment. These studies were primarily directed toward peak-shaving operations wherein the alternative was liquefied natural gas storage However, in these storage applications the end product was desired to be utilized as a gas fuel form for stationary industrial or pipeline utilization.
Vehicular utilization of natural gas continues to be frustrated by the need of service and refueling infrastructures because of continued focus on compressed natural gas utilization. Even though natural gas is a logical and common sense substitute for gasoline, the use of natural gas as compressed natural gas for vehicles has not been well received. The primary problem with the use of compressed natural gas is the weight, bulk and cost of pressure vessels. Limited mileage range and significant weight and space requirements of such compressed natural gas tanks generally limits the use of compressed natural gas to large vehicles such as buses and/or trucks. But even with the larger vehicles, the limited use, range and limited supply distribution systems has stagnated vehicular use of methane.
Utilization of the solubility of methane in for example, liquefied petroleum gas such as propane and butane has been expanded to include processes wherein liquefied natural gas is vaporized through heat exchange with liquid propane and then pipeline gas (methane) is dissolved in the propane, the liquid mixture then being vaporized for utilization. The procedure exploits the extreme cold of liquefied natural gas to cool down the propane by heat exchange, it being recognized that the cooling process is necessary as the solubility of methane and liquid propane increases with the decrease in temperature However, the prior art as represented by West German Offenlegungsschrift 243,819 disclosed Feb. 19, 1976 addresses the preparation of a methane liquid propane solution for the purposes of storage and transportation. The reference further allows that it is possible to mix air or nitrogen into the blended and vaporized propane with the gas air mixture being adjusted for end use as a propane substitute. The procedure is proposed as a solution wherein a limited quantity of propane in the form of liquid is available.
The forming of solutions of methane and liquefied petroleum gas to form a liquid for storage or transportation for later use as a gas fuel does not address the problems of using natural gas as an alternative fuel for gasoline for vehicular purposes. The utilization of refrigerated liquid fuels which incorporate substantial amounts of methane can provide all the known benefits of natural gas vehicles such as low polution emission and displacement of imported oil while minimizing institutional and economic barriers associated with these vehicles, by use of the liquid fuel solutions of methane as a liquid at the point of use. The liquid fuel solutions of methane and liquefied petroleum gas provides a technique to place methane in a liquid fuel for vehicle fuel usage without the full cost of liquefied natural gas liquefaction. Liquid fuel solutions are suitable for use in existing propane and butane infrastructure for delivery, storage and distribution.